GB1494366A - Straight bar knitting machine - Google Patents

Abstract

1494366 Automatic control INSTITUTE TEXTILE DE FRANCE and JAEGER 17 March 1975 [21 March 1974] 10940/75 Heading G3N [Also in Division D1] A yarn supply device for a straight-bar knitting machine having a cam bar 6 and a carrier bar 8 which perform linked reciprocating motions is controlled to feed the needles with yarn via carrier(s) 3 at a rate dependent on the required stitch size and comprises for each carrier 3 a yarn spool 11, a yarn feed unit comprising a driven pulley 13, a yarn take-up device 49 and a fixed yarn guide 48 in the median perpendicular plane P of the needle bar, and an electrical drive system for the pulley 13 whose speed is controlled in dependence on the positions and speeds of both bars 6, 8 so as to maintain the feed of yarn at the required level. Transducer assemblies 14, 15 generate through optical encoders 20, 21 pulses representing the speeds of the bars and through potentiometers 22, 23 D.C. signals representing their positions, the latter signals being used to amplitude-modulate the former at 54, 55. The signal from 23 is corrected at 37 - a pair of biased oppositely connected diodes - by a factor 1 Œ sin α, where α is the angle of carrier 3 relative to plane P. The signal from 22 and that from a potentiometer 30 representing the position of adjustable end stops 10 of bar 8 are compared at 42 to trigger an integrator 43 which generates a ramp voltage to give suitably accelerated and decelerated rotation of pulley 13 at the beginning and end of each course. A manual control 44 and a control 46 responsive to the position in the knitted fabric give adjustment of stitch length. A logic device 41 blocks the signals from 20 when cam bar 6 travels beyond the width of the knitted fabric. The outputs of 54, 55 are compared at 56 with a signal from 47 representing the actual speed of the pulley to produce an error signal which is amplified at 59 to control the drive motor 34. A circuit 60, 61 generates a tachometric damping signal for stability. A single motor 34 may drive several pulleys through belts or a common shaft. Instead of controlling the motor speed, the amplifier 59 may operate an electromagnetic coupling system including a drive coupler and a brake coupler between a constant speed motor and the pulley. The bars 6, 8 may be monitored by purely digital devices, digital-analogue converters providing the D.C. position signals.